When is it worth paying to guard your professional reputation online?

It might be best to simply ignore a negative review on Google Plus or an inflammatory comment on Twitter

Ask David Engel how many customers he has for Review Concierge, his service to protect and repair the online reputations of healthcare professionals, and he'll proudly say the number is around 300,000.

However, that's "honorary" customers — doctors, dentists and others who have been signed up for Review Concierge without even knowing it. They receive emails urging them to contact the San Diego company if negative comments or reviews are found online.

How many paying customers does Engel have? That number, he said, is closer to 1,500.

Reputation management is a fast-growing industry as review sites such as Yelp and Angie's List play an increasingly important role for businesses and consumers. Experts say a single negative comment can have lasting repercussions, from loss of business to career setbacks.

But are these reputation-management services for everyone? How do you know when it's time to bring in professional help?

Danny DeMichele, a Carlsbad Internet marketing consultant who assists clients with reputation-management issues, said the trick is knowing when a pro's input can make a difference.

Spending hundreds of dollars a month for a professional probably isn't worth it in all situations. There are some things you just can't fix.— Danny DeMichele, a Carlsbad Internet marketing consultant

"Spending hundreds of dollars a month for a professional probably isn't worth it in all situations," he said. "There are some things you just can't fix."

For example, DeMichele said, it might be best to simply ignore a negative review on Google Plus or an inflammatory comment on Twitter. Trying to address them could make matters worse.

But if it looks like a reputation-scorching brush fire is burning out of control online, he said, it can be wise to hire someone with experience handling a digital fire hose.

I wrote last week about an email from Review Concierge received by David Powell, a Los Angeles pediatric dentist. It warned that a grade of F had been found on a site called YellowBot and encouraged Powell to "create the online reputation that you deserve."

Review Concierge was willing to help — for a fee that could run anywhere from $20 to $200 a month.

Powell, who hadn't known he was one of Review Concierge's honorary customers, said he'd just ignore the YellowBot listing. But he acknowledged that "it's hard to know how seriously to take things like this."

Engel at Review Concierge said it can be perilous for healthcare professionals and other small-business owners to allow a negative comment to fester online.

"People research you on the Internet," he said. "It's important to know what's being said behind your back."

And that's true. But companies like Review Concierge, which says it can dispute negative comments and help generate positive reviews, offer little that people can't do themselves.

Andy Beal, author of "Repped: 30 Days to a Better Online Reputation," said Powell's situation was indicative of most reputation-related issues on the Internet: a relatively insignificant comment on a relatively insignificant website.

A key test of a negative review's potential influence, Beal said, is if it comes up within the first 20 results on a Google search of your name or the name of your business. If so, he said, that's a problem you'll want to address.

The bigger the problem — that is, the more it's hurting your business — the more reason to bring in a reputation-management professional who will oversee your response, Beal said.

A total cyber-image makeover can include disputing negative comments, promoting positive ones, setting up websites to get your story out there and an aggressive social-media campaign. Depending on how extensive such efforts are, Beal said, the cost can run tens of thousands of dollars.

"It takes a lot of work to change the perception of your reputation," he said.

There are a number of well-established players in the field, including Reputation.com and Brand.com. Most leading public-relations firms also offer reputation-management services.

Kerry Rego is the author of "What You Don't Know About Social Media CAN Hurt You: Take Control of Your Online Reputation." She said that although a professional might be able to provide helpful advice, many reputation-management services "are just fleecing people for thousands of dollars."

"I'm a consultant myself," Rego said. "But what I do is what most people can do."

Here are a few steps she advises:

• Google yourself to see what's out there and set up a Google Alert with your name so you'll be notified any time something new is posted.

• Establish your own Internet domain (such as DavidLazarus.com) so you'll have a place to present your side of the story or make a positive impression.

• Create your own content on sites such as Facebook, Twitter and YouTube. The goal is to tip the playing field in your favor any time someone searches for you online.

• Respond to negative reviews and comments, but do so carefully and politely.

"If you treat people right, your reputation will go up," Rego said. "Just making an effort will counter a lot of the negativity out there."

She also advised that people have reasonable expectations about how much they can control what others say about them online.

"There's no way to remove all the negativity from the Web," she said. "All you can do is try to bury it as best you can with positive thoughts."